And Twobob : , but I just can't figure out why I could not access the kindle. I redid what I did before and this time it worked. It was silent around me, that might have done the trick. Did not go over wifi though.

@ixtab:
The diags. partition is already mounted.
Either an earlier un-mount command was missing (or more likely) had not yet completed.
Reasons for the un-mount not to have completed:

The script had written something to the diags partition, but the writes had not competed (eMMC writes slower than the script runs).

The script still had a file open on the diags partition (or the diags partition was the current directory).

What to do about it (will take a bit of testing since Busybox may not behave the same as the full umount command) -

In sections of the script (since it has section selection, it probably has compete open, do-something, close sequences).

Where the script now has: "umount ..." commands -
Which will fail if writes have not completed, do -

mount -o remount /mnt/mmc
**OR**
mount -o remount /dev/mmcblk0p2

(Depending on which it the problem - blk0p2 still mounted or /mnt/mmc still busy).

NOTE: There is no option following the remount command, that is not a typo! Used
without a "ro" or "rw" option to the remount command will cause all buffered writes to complete.
AND the command will block (not return) until the eMMC catches up.

Once that special version of the mount command (completes and) returns, THEN issue the umount command.

*** At least that is the expected behavior of full version of umount ***
*** If the Kpw doesn't have the full version, you will have to test if the Busybox version behaves the same. ***